The invention relates to a method of localizing a deviant region in a turbid medium that is represented by a set of volume elements, which method includes a first measuring step in which the turbid medium is irradiated by means of light comprising radiation of mainly a fist wavelength and in which intensities of a part of the light comprising radiation of mainly the first wavelength that is transported along a plurality of light paths through the turbid medium are measured, and an imaging step for reconstructing an image of the turbid medium from the measured intensities.
The invention also relates to a device for carrying out such a method.
In the context of the present application the term light is to be understood to mean electromagnetic radiation of a wavelength in the visible or infrared range between approximately 400 and 1400 nm. A turbid medium is to be understood to mean a substance consisting of a highly light dispersive material. More specifically, in the context of the present application the term turbid medium is to be understood to mean biological tissue. A deviant region is to be understood to mean a region in which the turbid medium deviates in any way or form from the turbid medium in the surrounding region. More specifically, in the context of the present application such an area is to be understood to mean a region comprising tumor tissue. The turbid medium is represented by a set of volume elements. Volume elements of this kind are also known as voxels. The size and shape of the volume elements may be the same for all volume elements. However, it is alternatively possible for the volume elements to have mutually different dimensions and shapes.
A method and a device of this kind are known from “Clinical Optical Tomography and NIR Spectroscopy for Breast Cancer Detection”, S. B. Colak et al, IEEE Journal of Selected Tops in Quantum Electronics, Vol. 5, No. 4, July/August 1999. The known method and device are used for imaging the interior of biological tissues. The method and the device can be used inter alia in medical diagnostics for in vivo breast examinations for visual localization of any tumors present in the breast tissue of a human or animal female body. According to the known method a turbid medium is successively irradiated by light from various irradiation positions. Subsequently, the intensity of the light having been transported along different light paths through the turbid medium that extend from their irradiation position is measured in a number of measuring positions. The intensities measured are used for the reconstruction of an image of the turbid medium. A spatial distribution of the attenuation of the light through the tissue is reproduced in this image. Light is attenuated by tissue in that the tissue disperses and absorbs the light.
A possibly deviant region can be visually localized in the image if the attenuation of the light by the tissue in the deviant region deviates sufficiently from the attenuation of the light by the tissue in the surrounding region. A plurality of individual images can be formed by carrying out the known method repeatedly while using light of different wavelengths.
The known method and device have a drawback in that the images thus obtained are insufficiently clear so as to enable accurate visual localization of deviant regions.